Internal displacements of spherical shells subjected to steady sound waves
in water have previously been computed by other researchers [R. Hickling et
al., J. Acoust. Soc. Am. 92, 499 (1992)]. Such displacements can be difficult
to interpret with a guided wave representation because of the superposition of
counterpropagating Lamb waves and the local response to the incident wave. In
this research the surface displacements of a cylinder were evaluated since they
can be mathematically decomposed into counterpropagating circumferential
traveling waves. (Unlike an analogous decomposition for spheres, the amplitudes
in the cylinder case are regular at 0 and 180 deg.) By limiting attention to
the radial displacements of the outer surface, it was also possible to display
the response to short-tone bursts and thereby distinguish between the local
response to the incident acoustic wave and Lamb waves launched on the shell.
Both the steady-state and burst response situations clearly manifest waves
launched on the shell. These can be easily seen for ka as low as 8 for a thin
shell. [Work supported by ONR.]